Reducing Secondary Flow Losses in Low-Pressure Turbines With Blade Fences. Part II: Experimental Validation on Linear Cascades

This paper deals with the design of passive control devices for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. A novel kind of device is introduced which consists of shelf-like fences to be added to the blade surface. Such a device is intended to harm the development of secondary flows, thus reducing losses and flow turning devi-ation with respect to the naked blade. In this second part, an experimental campaign on a linear cascade is presented which is aimed at proving the beneficial im-pact of the blade fences. Experiments were carried out on a low-speed test-rig, equipped with a large scale blade representative of the stators of the engine-like environment considered in part I. Measurements are mainly focused on the stator losses and on the flow field at the stator exit. The performance of the blade fences were evaluated by comparing the naked cascade and the fenced ones. The measurements highlighted the impact of the blade fences on the development of the secondary flows, affect-ing both the stator losses and the non-uniformity of the flow field over the exit plane, which, in the actual stage environment, im-pacts the operation of the downstream blade row. Moreover, the comparison between CFD and experiments proved the accuracy of the CFD setup, thus suggesting its reliability in predicting the stage performance in the engine-like configuration.